The discussion below is merely provided for general background information or exemplary environments, and is not intended to be used as an aid in determining the scope of the claimed subject matter.
The measurement of loads, both forces and moments, with accuracy and precision is important to many applications. A common use, where several moments and forces need to be measured, is in the testing of specimens in a wind tunnel. Test specimens can be placed on a platform balance located in a pit of the wind tunnel. The platform balance can be adapted to receive a vehicle or other large test specimens, rather than merely a scale model of the vehicle. Actual vehicles, rather than scale models of the vehicles, allow the designer to determine actual measurements of prototypes, rather than merely inferential measurements. If the test specimen is a vehicle with wheels, the platform balance can be equipped with a rolling belt to rotate the wheels, which can make a significant improvement in measurement accuracy and simulate real world environments.
Up to six components of force and moment act on a test specimen on the platform balance in the wind tunnel. If six components are present, they are typically referred to as lift force, drag force, side force, pitching moment, yawing moment, and rolling moment. The moments and forces that act on the test specimen are usually resolved into three components of force and three components of moment with transducers that are sensitive to the components.
With a vehicle placed on the platform balance, the combined weight of the vehicle, specimen support frame and rolling belts to drive the wheels can easily be tens of thousands of pounds. Typically, a counterbalance is provided to support the static weight of these components. In this manner, the transducers need not be designed to support the static weight, but rather, can be designed to resolve small forces. In order to allow the transducers to detect these small forces, the counterbalance must be compliant for the small forces. Although counterbalances have been used in the prior art, there is a continuing need for improved counterbalances, which in effect, allows the transducers of the platform balance to resolve even smaller forces.